Is incorrect what Thirsting Blade affirms that would be the rule without it? [closed]

By RAW:

"Thirsting Blade

Prerequisite: 5th level, Pact o f the Blade feature

You can attack with your pact weapon twice, instead of once, whenever you take the Attack action on your turn."

So, by RAW: If it says "instead", then otherwise (A.K.A. without that eldrich invocation) the rule would be: "You can attack with your pact weapon once whenever you take the Attack action on your turn."

But the "original" rule is not this, you can’t "attack with your pact weapon once whenever you take the attack action", actually, you can attack with your pact weapon once when you take the attack action AND choose to attack with your pact weapon. So, is incorrect what that invocation affirms that would be the rule without it?